Diabetic morbidity and mortality is largely a result of complications involving microvascular occlusive events. Furthermore, transmembrane phospholipid asymmetry in human diabetic red blood cells is perturbed; aminophospholipids are found in increased quantity in the plasma membrane outer monolayer. We have duplicated this effect in vitro by treating non-diabetic red cells with hyperglycemic concentrations of glucose. The glucose-induced loss of asymmetry is a result of an oxidant-mediated increase in passive lipid flip-flop. Current studies are aimed at determining the chemical and physical mechanisms mediating this membrane perturbation. New strategies for the prevention and treatment of cardiovascular complications in diabetics may result this work. Measurements of lipid flip-flop have required the synthesis of phospholipids with short acyl chains. The analysis of these lipids has been performed by FAB-MS and exact mass measurement.